The present invention relates to a height adjusting mechanism for swivel chair, and more particularly to a height adjusting mechanism for swivel chair in which a tightening phenomenon is avoided and an adjusted position is not changed, and an assembling is possible by a simple insertion fitting manner by utilizing a clip so that a manufacturing property and productivity can be improved.
A lift of swivel chair is an adjusting mechanism for appropriately adjusting the height of a seating plate in accordance with a body condition of a user, and various kinds of such adjusting mechanisms have been developed and used heretofore. For instance, a telescopic type and a screw type are mainly widely used, and these mechanisms are made in general to adjust a desired chair height by additionally providing to a column which is uprightly provided between a seating plate of the chair and legs whereby providing a height of the seating plate. Such column usually comprises a supporting pillar pipe and a cylinder pipe which bears the seating plate and is coupled by insertion fitting manner so as to be freely lifted and dropped within the supporting pillar pipe, and a chair height adjusting mechanism is additionally provided within this supporting pillar adjusting body so that a desired adjusting operation is obtained. The adjusting mechanism provided as these comprise some mechanical elements consisting of a screw, a clutch function for connecting or disconnecting a power transmission and a spring for returning this clutch to an original state so that the height adjustment is obtained. More particularly, it is constructed so as to connect or disconnect the lifting or dropping force by the clutch function by utilizing a difference between the load values where an occupied load is applied or not applied to the seating plate of the chair, and when an occupied load is applied to the chair, the cylinder pipe is dropped down and simultaneously the spring is compressed and a clutch mechanism coupled in screw manner with a screw shaft is released whereby a nut clutch is disconnected from the cylinder pipe whereby becomes to be an idle rotation without transmitting the rotating force of the seating plate to the nut clutch so that the height adjustment of the chair is not made, and on the contrary, in case of a state that a person does not seated on the chair, i.e., in case when a load is excluded, the cylinder pipe which has been dropped down by the returning force of the spring is returned to an original state and becomes to couple the clutch mechanism, and at the same time, the nut clutch and the cylinder pipe are made to be integral whereby a rotating force of the seating plate is transmitted to the nut clutch through the cylinder pipe, and the transmitted rotating force as these rotates the nut clutch, and the nut clutch is moved to up or down ward along with the screw so that a desired chair height adjustment can be obtained. For instance, a Japanese utility model official publication No. Sho-55-34846 and a U.S. Pat. No. 3,991,965 can be cited.
However, these adjusting mechanisms lift up the cylinder pipe by a returning force of the spring as in the above description in a state that an occupied load is excluded on the seating plate, and this lifting displacement makes the rotating force of the seating plate to be transmitted through the cylinder pipe when the clutch mechanism is coupled and the seating plate is rotated to right or left direction whereby the nut clutch is lifted up or dropped down to up or down ward along with the screw shaft in response to the rotating direction so that the chair height is made to be adjusted, and at this moment, when the seating plate is further rotated in a state that the nut clutch is reached to a uppermost end or to a lowermost end of the screw shaft due to a carelessness of a user, the nut clutch makes a tightening phenomenon at the uppermost end of the screw shaft and thereby a troublesome to have this to release again is accompanied, and since it is released by applying an instantaneous shock to the nut clutch in a reverse direction of tightening force upon releasing of the nut clutch operated with this tightening force, there has been a problem that it gives a unreasonableness to the mechanical elements and causes a factor of damage.
And, when an occupied load is applied to the chair and the clutch mechanism is released, the nut clutch becomes to be placed to a free state, and at this moment, when a shock or vibration of exterior is applied to the chair, the nut clutch which has been screw-coupled with the screw shaft can not maintain the adjusted current position and the position would be changed little by little whereby the chair height adjusting position is made to be changed, and therefore there has been a defect that the adjusted height is changed at every time changing the chair height adjusting position and seating on the chair and thereby the re-adjusting operation has to be made, in other word, the adjusting state of the chair is not made to be stable. And therefore, in order to solve the problem as described above, a lifting and dropping adjusting mechanism for swivel chair (Korean utility model official publication No. 91-5145) added with a tightening structural elements is developed and used in which a washer is provided at a bottom of a thrust bearing which is interposed between the nut clutch and the spring, a upwardly opened retaining circular groove is defined within an interior of the nut clutch, a rubber O-ring is provided such that a portion comes up to a upper surface of this retaining groove whereby the rubber O-ring is compressed by an expanding force of the spring transmitted through the washer and biting the screw shaft by a tightening force produced upon contracting of its inner diameter so that the nut clutch is fixed not to be so easily changed. This lifting and dropping adjusting mechanism has obtained a little effect for avoiding an alteration of the clutch, but the tightening force of the rubber O-ring is greatly operated unnecessarily, therefore there has been a defect that the lifting and dropping adjustment of the nut clutch upon adjusting the height is not smooth.
And, as described above, since a washer (holding ring) for compressing and expanding the rubber O-ring has to be necessarily provided at upper side of the nut clutch (height adjusting means), the mechanical elements are increased, and since this fixing space of the mechanical elements are necessarily required, there has been a defect that the volume of the device becomes bigger, but also there has been a problem in improving the productivity because expense for materials and assembling process number become more. And, since the compressing and expanding value of the rubber O-ring becomes different in accordance with that the occupied load being applied or not, its tightening force also becomes to have difference a little in accordance with the operation of the occupied load, and the tightening state of the rubber O-ring is released in a state that the occupied load is released whereby the nut clutch is moved little by little from the screw in case when the external force is applied, and such movement has caused a defect to change the adjusted position. And, a release stopping polygonal nut for automobile which suppresses the releasing of nut by interposing a ring which is big in frictional resistance to a nut to be coupled with the screw shaft has been also already widely known.
Therefore, recently the applicant of this application has previously filed an application of a height adjusting mechanism of swivel chair in which the height adjusting function is made to be smooth by a simple construction in which a clutch recess is defined at a central portion of interior of the nut clutch to be screw-coupled to the screw shaft and a rubber ring is inserted to said recess in a structure as described above.
On the other hand, the screw shaft for directly providing a height of the chair among the adjusting mechanism is firmly fixed to a bottom surface such that a movement and rotation are prevented in an axial direction of the screw shaft and an orthogonal direction to the axial direction, and such fixing method is carried out by integrally providing a piercing through bar having a predetermined diameter at an end portion of the screw shaft, this screw shaft's piercing through bar is passed toward exterior through a passing through hole perforated at a bottom center of the supporting pillar pipe, and then its projected piercing through bar and the bottom surface of the supporting pillar pipe are welded at the exterior. However, since this fixing method necessarily requires a welding process, much working time period and many processes are required, and accordingly not only there has been a defect that a manufacturing property as well as mass productivity are worse, but also there has been a nonproductive and uneconomical problem that in case when a part is damaged in partial, i.e., in case when screw tips of the crew shaft are damaged, the supporting pillar pipe itself has to be changed.